The mechanism by which carcinogens selectively interact with processes responsible for the synthesis and processing of ribosomal RNA and messenger RNA will be examined in normal and regenerating liver. The capacity of N-hydroxy-2-acetylaminofluorene to affect nuclear rRNA and heterogeneous RNA synthesis via nucleolar RNA polymerase and nucleoplasmic RNA polymerase, respectively, will be studied. In vitro assessment of the ability of N-acetoxy-2-acetylaminofluorene to modify the template activity of DNA for hepatic nuclear RNA polymerase and DNA polymerase will also be undertaken.